JP2006023123A - Defect inspection method and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a defect inspection method and its device for surely detecting a defect occurring at a prescribed position of an article. <P>SOLUTION: This defect inspection method is used for inspecting, as a defect, existence or absence of a linearly extending hollow part 11, appearing at the prescribed position on a surface under inspection of the article 2. The method is provided with first and second imaging processes for imaging the surface. Prior to the second imaging process, an angle detection process is done for detecting the turning angle of the article 2 centering on a perpendicular line passing through the center of the surface. Then, a projection direction calculation process is done for calculating a light projection direction crossing the longitudinal direction of the hollow part. In the second imaging process, a light projection process is done for projecting directional light inclining from a direction calculated in the calculation process toward the surface. After the second imaging process, an inspection image generation process is done for extracting an area where the defect occurs from an image obtained in the second imaging process to generate an inspection image. Then, a determination process is done for determining whether or not the defect exists from the inspection image. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a defect inspection method and apparatus for inspecting whether or not a defect occurs at a predetermined position on a surface to be inspected of an article.

  As an article to be inspected in this type of defect inspection, for example, a so-called steion in which a tab is attached to a panel via a rivet and a break opening formed in a part of the panel is opened by a swinging operation of the tab. A tab type can lid is mentioned. The can lid has a score carved along the fracture shape of the fracture opening. The score is formed between the rivet and the peripheral edge of the panel, and the tip of the tab faces the break opening through a part of the score close to the rivet.

  By the way, in the can lid, when a part of the score is inadvertently broken and cracked, the inside of the can body is sealed even if the can lid is wrapped around the can body filled with the contents. Can not do it. Therefore, it is inspected whether or not a crack has occurred in the score. Conventionally, as a score crack inspection, a method of detecting light leakage to the other side by irradiating light from one side of the front and back of the can lid is known (for example, see Patent Document 1). According to this method, when a crack is generated in the score, light that has passed through the crack is detected from one side of the front and back of the can lid, so that the presence or absence of the crack can be easily inspected.

However, in this type of can lid, when the tab is attached to the rivet, the score formed along the rivet may crack. And the score formed along the rivet is covered by the tip of the tab, so even if light is irradiated from one side of the front and back of the can lid, the light is blocked at the tip of the tab and there is no crack There is an inconvenience that cannot be detected.
JP 2000-193426 A

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a defect inspection method and apparatus capable of reliably detecting a defect occurring at a predetermined position of an article by eliminating such inconvenience.

  In order to achieve such an object, the present invention provides a defect inspection for inspecting the presence or absence of a defect having an indented portion that occurs in a predetermined position on the surface to be inspected as a defect on an article having the surface to be inspected. A method for detecting a rotation angle of an article about a normal passing through the center of a surface to be inspected based on a first imaging step for imaging the surface to be inspected and an image obtained by the first imaging step. The angle detection step to be performed and the direction intersecting the longitudinal direction of the indented portion to be defective are set as the light irradiation direction, and the light irradiation direction to the inspection surface is calculated from the angle detected by the angle detection step. An irradiation direction calculation step, a light irradiation step of irradiating light having directivity inclined toward the surface to be inspected from the direction calculated by the irradiation direction calculation step, and the illumination illuminated by the light irradiation step Second to image the surface to be inspected Based on an image process, an inspection image generation process for generating an inspection image by extracting a region where the defect occurs from an image obtained by the second imaging process, and an image generated by the inspection image generation process, And a determination step of determining the presence or absence of the defect.

  The present inventor, when inspecting the presence or absence of a defective indentation that extends linearly at a predetermined position on the surface to be inspected of the article, intersects the longitudinal direction of the indented portion considered to be defective (preferably orthogonal) It was found by various tests that high-intensity reflection was observed in the depressions by irradiating light from the direction in which the image was processed, and that even fine line-like depressions could be confirmed by image processing. By the way, although the indented portion that is considered to be defective occurs at a predetermined position on the surface to be inspected of the article, the orientation of the surface to be inspected of the article (that is, the state rotated around the perpendicular passing through the center of the surface to be inspected) If it is, the direction of the light irradiated to a hollow part cannot be defined.

  Therefore, according to the defect inspection method of the present invention, first, the surface to be inspected of the article is imaged by the first imaging step. Next, the angle detection step detects the rotation angle of the article around the perpendicular line passing through the center of the surface to be inspected. Then, the irradiation direction of the light to the surface to be inspected is calculated by the irradiation direction calculation step. Thereby, in the said light irradiation process, the light which inclines toward the said to-be-inspected surface from the direction calculated by the irradiation direction calculation process can be irradiated.

  And the to-be-inspected surface of the articles | goods illuminated by the light irradiation process by the 2nd imaging process is imaged, The area | region where a defect generate | occur | produces by the said test | inspection image generation process is extracted from this image, and a test | inspection image is produced | generated. At this time, if there is a dent that is considered to be defective on the surface to be inspected, the dent that has been made bright by the light irradiation process in the inspection image can be confirmed, and the dent that is determined to be defective by the subsequent determination process can be confirmed. Presence / absence can be determined.

  As described above, according to the present invention, light can be reliably transmitted from a direction that intersects the longitudinal direction of the indented portion, regardless of the rotation direction about the perpendicular line passing through the center of the article. Since it can irradiate, the presence or absence of a hollow part can be determined reliably in the determination step.

  Further, in the light irradiation step of the method of the present invention, the light irradiated from the direction calculated in the irradiation direction calculation step is a plurality of light sources arranged in an annular shape corresponding to the periphery of the surface to be inspected of the article. It is the light obtained by lighting only the light source corresponding to the direction calculated by the said irradiation direction calculation process by the illumination means which can light up each light source selectively.

  According to this, it is only necessary to select and turn on only the light source corresponding to the direction calculated by the irradiation direction calculation step from among a plurality of light sources, and the control can be performed very easily.

  Further, in the light irradiation step of the method of the present invention, other light having a light amount smaller than the light irradiated from the direction calculated by the irradiation direction calculation step is irradiated from a position facing the surface to be inspected. Is preferred. When light is irradiated from the direction intersecting the longitudinal direction to the indented portion that is considered to be defective, the light from that direction also hits other unevenness formed on the surface to be inspected. A shadow is generated. In this case, for example, when extracting a region where a defect occurs in the inspection image generation process, even if it is attempted to determine the coordinates of the region to be extracted with reference to other unevenness, the accuracy of the coordinate is reduced due to the influence of the shadow. There is a risk. Therefore, by irradiating other light having a light amount smaller than the light irradiated from the direction calculated by the irradiation direction calculating step from the position opposite to the surface to be inspected, other light formed on the surface to be inspected Shadows caused by unevenness and the like can be made small, and the region extraction by the inspection image generation process can be performed with high accuracy.

  In the method of the present invention, the article is transported along a transport path, and the first imaging step is performed on the article transported to a predetermined position along the transport path. The light irradiation step and the second imaging step are performed on an article conveyed to a downstream position through a step. Thereby, even if the article is transported in the direction rotated in any direction, light can be irradiated from the direction intersecting the longitudinal direction of the hollow portion which is regarded as defective in the light irradiation step, Since the determination process can be performed, the efficiency of the inspection can be dramatically improved.

  In addition, the present invention provides a presence / absence of a defect, which is provided in a conveyance path for conveying an article, with a hollow portion extending in a linear shape generated at a predetermined position on an inspection surface of the article conveyed along the conveyance path as a defect. A defect inspection apparatus for inspecting, comprising: a first imaging unit that images a surface to be inspected of an article conveyed on the conveyance path; and a center of the surface to be inspected based on an image obtained by the first imaging unit. An angle detection means for detecting the rotation angle of the article with the passing normal as an axis; and an inspection surface of the article which is provided on the downstream side of the first imaging means and is conveyed through the first imaging means. The illumination device is capable of irradiating light having directivity that is selectively inclined from any one of the surroundings of the surface toward the surface to be inspected, and the failure is determined from the angle detected by the angle detection device. Calculate the direction that intersects the longitudinal direction of Illumination control means for controlling the illuminating means with the direction as the light irradiation direction on the surface to be inspected of the article, second imaging means for imaging the surface to be inspected of the article illuminated by the illuminating means, And a determination unit that extracts an area where the defect occurs from an image obtained by the imaging unit to generate an inspection image, and determines the presence / absence of the defect based on the generated image.

  In the defect inspection apparatus of the present invention, when the article is being conveyed along the conveyance path, first, the surface to be inspected of the article is imaged by the first imaging means. Next, the angle detection means detects the rotation angle of the article about the perpendicular passing through the center of the surface to be inspected. Subsequently, when the article is conveyed downstream, the illumination unit irradiates light that is inclined toward the surface to be inspected from any one of the surroundings of the surface to be inspected. At this time, the illuminating unit irradiates light from a direction intersecting with the longitudinal direction of the hollow portion which is regarded as defective under the control of the illumination control unit. Thereby, based on the detection result of the angle detection means, the direction of the article being conveyed along the conveyance path is directed in any direction by rotation about a perpendicular passing through the center of the surface to be inspected. It is possible to reliably irradiate light from a direction intersecting the longitudinal direction of the depression.

  When light is irradiated from a direction intersecting with the longitudinal direction of the dent portion, which is regarded as defective, high-intensity reflection is seen in the dent portion as described above. Here, the surface to be inspected of the article illuminated by the illumination unit is imaged by the second imaging unit, and the determination unit extracts the region where the defect occurs from the image of the second imaging unit and generates an inspection image. The presence / absence of the defect is determined based on the generated image.

  Thus, according to the defect inspection apparatus of the present invention, when the article is being conveyed along the conveyance path, the inspection surface of the article is in any direction of the rotation direction with the perpendicular passing through the center as the axis. Even if it exists, light can be reliably irradiated from the direction which cross | intersects the longitudinal direction of a hollow part, and the presence or absence of the hollow part by the said determination means can be determined reliably. In addition, a defect inspection can be performed while the article is being conveyed, and the inspection can be performed efficiently.

  In the defect inspection apparatus of the present invention, the illumination unit includes a plurality of light sources that are arranged in a ring and can be individually lit, and the illumination control unit calculates based on the angle detected by the angle detection unit. Only the light source corresponding to the direction intersecting with the longitudinal direction of the recessed portion that is regarded as defective is turned on.

  According to the illuminating means, since the plurality of light sources are arranged in a ring and can be individually turned on, it is possible to reliably irradiate light from a desired direction toward the inspection surface of the article with a simple structure. Thereby, based on the angle detected by the angle detection means, only the light source corresponding to the direction intersecting with the longitudinal direction of the defective recess can be turned on to reflect the recess with high brightness. .

  In the defect inspection apparatus of the present invention, another illumination unit that irradiates light having a light amount smaller than that of the illumination unit from a position opposite to the surface to be inspected is provided at the position where the illumination unit is provided. Is preferred. By irradiating light from the direction intersecting the longitudinal direction to the hollow portion which is regarded as defective by the illuminating means, and simultaneously irradiating light from a position opposite to the inspected surface by other illuminating means, Shadows such as irregularities other than the depressions can be made small. At this time, since the amount of light of the other illumination means is smaller than that of the illumination means, the high-intensity reflection of the defective recess is not obstructed, and the region where the defect occurs by the determination means is extracted. In addition, the presence / absence of a defect can be determined with high accuracy.

  In addition, as an article to be inspected by the defect inspection method and the defect inspection apparatus of the present invention, a tab is fixed to a panel surface via a rivet, and a score is set at a position where the tip of the tab between the peripheral edge of the panel and the rivet faces. A thin plate-shaped can lid having a rupture opening formed so as to be ruptureable is mentioned. This can lid is called a steion tab type can lid. In this can lid, when the score is broken or has a tendency to break, a linear depression along the score is formed on the back surface of the can lid. And a linear hollow part irradiates the light which has directivity from the direction which cross | intersects the longitudinal direction, and this light reflects with high brightness | luminance. Therefore, the back of the panel of the can lid is the surface to be inspected, and the defect is a linear depression formed along the broken score along with the breaking of the score of the portion extending adjacent to the rivet. The break of the score of the portion extending adjacent to the rivet in the can lid, which could not be inspected conventionally, can be reliably inspected by the defect inspection method and the defect inspection apparatus of the present invention.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of a defect inspection apparatus according to the present embodiment, FIG. 2 is an explanatory perspective view of a main part, FIG. 3 is an explanatory diagram showing a schematic configuration of illumination means, and FIG. 4 is a defect according to the present embodiment. FIG. 5 is an explanatory diagram showing a reference image of the back surface of the can lid, FIG. 6 is an explanatory diagram showing an image of the can lid to be inspected, and FIG. 7 is a cross-sectional explanatory diagram of a part of the can lid. 8 is an explanatory view showing an inspection image, FIG. 9 is an explanatory plan view showing the front side of the can lid, and FIG. 10 is an explanatory plan view showing the back side of the can lid.

    As shown in FIG. 1, the defect inspection apparatus 1 of the present embodiment is provided along a conveyance path 3 that conveys the can lid 2. The can lid 2 in the transport path 3 is transported with its back side facing upward. In addition, as shown in FIG. 1, the direction of the can lid 2 in the conveyance path 3 (a state rotated around a perpendicular passing through the center of the front and back surfaces of the can lid 2) is uneven.

  As shown in FIG. 9, the can lid 2 has a rivet 4 formed at a substantially central portion of the front side surface thereof, and a tab 5 is fixed through the rivet 4. The tab 5 has a front end 5a facing a break opening 7 formed so as to be breakable by a score 6. The tab 5 swings by pulling up the rear end 5b of the tab 5, and the break opening 7 breaks. It can be done. Further, the can lid 2 is formed with a plurality of irregularities such as the rivet 4, a protrusion 8 for preventing the rotation of the tab 5, and a recess 9 for accommodating the tab 5. These irregularities are shown in FIG. 10. Thus, the inverted unevenness is formed on the back side surface of the can lid 2.

  The defect inspection apparatus 1 according to the present embodiment collects an image using the back side surface of the can lid 2 conveyed along the conveyance path 3 as a surface to be inspected, and a part of the score 6 adjacent to the rivet 4 by this image processing. The defect of the can lid 2 is inspected by detecting a crack (including a state in which the crack is likely to be generated) as a defect. Here, the defect detected in the present embodiment will be described. As shown in FIG. 7A, the score 6 adjacent to the rivet 4 is covered with the tab 5 and is difficult to confirm from the front side surface of the can lid 2. On the other hand, on the back side surface of the can lid 2, as shown in FIG. 7B, when a crack 10 occurs in the score 6 adjacent to the rivet 4, the score 6 is increased between the crack 10 and the rivet 4. A linear depression 11 along the line is formed. Therefore, if such a depression 11 is detected by image processing, it can be confirmed that a crack 10 has occurred in the score 6. By the way, although such a hollow part 11 is formed in a very fine linear shape, by irradiating the light which has directivity from the direction which cross | intersects the longitudinal direction of the hollow part 11 shown by the arrow in FIG.7 (b). As shown in FIG. 8, high-intensity reflection is generated in the hollow portion 11 and can be clearly highlighted, based on the knowledge of the present inventor.

  First, the configuration of the defect inspection apparatus 1 of the present embodiment will be described. As shown in FIG. 1, the defect inspection apparatus 1 includes a first imaging unit 12 that captures an image of the can lid 2 that is transported along the transport path 3, and a second that is located downstream of the first imaging unit 12. And imaging means 13. The image picked up by the first image pickup means 12 is processed by the angle detection means 14. The image captured by the second imaging unit 13 is processed by the determination unit 15. A first illumination unit 16 is provided between the first imaging unit 12 and the conveyance path 3, and a second illumination unit 17 and a third illumination are provided between the second imaging unit 13 and the conveyance path 3. Means 18 are provided. The second illumination means 17 is controlled by the illumination control means 19.

  As shown in FIGS. 1 and 2, the first illumination means 16 employs ring illumination, and illuminates the back side surface of the can lid 2 flatly when the first image pickup means 12 takes an image. The second illuminating means 17 is the illuminating means of the present invention, and as shown in FIG. 3, a plurality of light emitting portions 20 having the same width are arranged in a ring shape, and each light emitting portion 20 can emit light independently. ing. Each light emitting unit 20 includes a plurality of LEDs 21 as a light source having directivity. By causing any of the light emitting portions 20 to emit light during imaging by the second imaging unit 13, the can lid can be viewed from a desired direction in the radial direction of the can lid 2 with respect to the can lid 2 directly below the second illumination unit 17. The light which inclines toward 2 can be irradiated. The third illuminating means 18 is another illuminating means of the present invention, and employs ring illumination as shown in FIG. The third illuminating unit 18 illuminates the back side surface of the can lid 2 with a light amount that does not hinder the illumination by the second illuminating unit 17 during imaging by the second imaging unit 13.

  In addition, as shown in FIGS. 1 and 2, the transport path 3 includes a first trigger sensor 22 that senses that the can lid 2 is positioned immediately below the first imaging unit 12, and the can lid 2 performs the second imaging. There is provided a second trigger sensor 23 for sensing that it is located immediately below the means 13. The first trigger sensor 22 includes a light projecting unit 22a and a light receiving unit 22b facing each other via the transport path 3, and the transported can lid 2 blocks the light of the light projecting unit 22a so that the can lid 2 is blocked. Detect. Similarly to the first trigger sensor 22, the second trigger sensor 23 includes a light projecting unit 23a and a light receiving unit 23b.

  Next, the operation of the defect inspection apparatus 1 having the above configuration will be described. When the conveyance of the can lid 2 along the conveyance path 3 is started, the operation of the defect inspection apparatus 1 is started. When the can lid 2 is detected by the first trigger sensor 22 in STEP 1 of FIG. 4 and the first trigger signal is output, the process proceeds to STEP 2 of FIG. 4 and the can lid 2 illuminated by the first illuminating means 16 is detected. The back side surface is imaged by the first imaging unit 12, and the image is captured by the angle detection unit 14 (first imaging step).

  Next, proceeding to STEP 3 in FIG. 4, the rotation angle of the article about the perpendicular line passing through the center of the surface to be inspected is detected by the angle detection means 14 from the captured image. At this time, in this embodiment, a template matching method or a pattern matching method is adopted. That is, the angle detection means 14 stores in advance an image 24 of the back side of the can lid 2 oriented in a reference direction as shown in FIG. 5, and the can taken in STEP 2 as shown in FIG. The degree of coincidence with the image 25 on the back side surface of the lid 2 is evaluated, and the rotation angle θ is obtained from the coordinate having the highest degree of coincidence (angle detection step). In the present embodiment, a normalized correlation method is used for determining the degree of coincidence. Next, proceeding to STEP 4 in FIG. 4, the angle detection means 14 temporarily stores the detected angle.

  Subsequently, the can lid 2 is conveyed along the conveyance path 3, and when the can lid 2 is detected by the second trigger sensor 23 in STEP 5 of FIG. 4 and the second trigger signal is output, the conveyance path 3 is moved to the can lid. The angle detected from the angle detection means 14 is input to the illumination control means 19 in synchronization with the speed at which 2 is conveyed. Then, proceeding to STEP 6 in FIG. 4, the illumination control means 19 calculates the irradiation direction of the light to the can lid 2 corresponding to the angle detected from the angle detection means 14 (irradiation direction calculation step). The irradiation direction of the light calculated at this time is a direction indicated by an arrow in FIG. 8, and is a direction that intersects (preferably perpendicularly) the longitudinal direction of the defective recess 11. Next, the process proceeds to STEP 7 in FIG. 4, and the illumination control unit 19 selects and lights up the light emitting unit 20 corresponding to the calculated irradiation direction among the light emitting units 20 of the second illumination unit 17 as shown in FIG. 3. Let In FIG. 3, a plurality of (four) light emitting units 20 are lit, but a single light emitting unit 20 may be lit. Thereby, the light from the selected light emitting unit 20 of the second illumination unit 17 is irradiated to the back side surface of the can lid 2 located immediately below the second imaging unit 13 (light irradiation step). At the same time, light having a light amount smaller than the light emitted from the second illumination means 17 is emitted from the third illumination means 18 to the can lid 2 in a planar shape.

  Next, proceeding to STEP 8 in FIG. 4, the back side surface of the can lid 2 illuminated by the second illumination means 17 and the third illumination means 18 is imaged by the second imaging means 13, and the image is taken into the determination means 15 ( Second imaging step). The determination unit 15 proceeds to STEP 9 in FIG. 4, and first, from the image captured by the second imaging unit 13, as shown in FIG. 8, the score 6 near the rivet 4, which is the position where the depression 11 is generated. The inspection image 26 is generated by extracting a predetermined area including (inspection image generation step).

  Subsequently, the process proceeds to STEP 10 in FIG. 4, and the determination unit 15 determines the presence or absence of the depression 11 based on the inspection image 26 (determination step). That is, when the depression 11 is generated in the vicinity of the rivet 4, an inspection image in which the depression 11 is white-reflected with high brightness is obtained by irradiating light from the second illumination means 17 to the generation position of the depression 11. It is done. And the determination means 15 binarizes the said test | inspection image, and determines as a defect, when the pixel number of the white part of the hollow part 11 exceeds the predetermined upper limit. Then, the process proceeds to STEP 11 in FIG. 4, and the determination unit 15 outputs a signal related to the determination result of the can lid 2. Note that the can lid 2 determined to be defective by the determination means 15 is discharged by a discharge means (not shown) provided downstream of the transport path 3 in response to the output signal in STEP 11 of FIG.

  Thus, according to the defect inspection apparatus 1 of the present embodiment, the score 6 in the vicinity of the rivet 4 is provided in the conveyance path 3 that is dispensed and conveyed after the tab attachment process of the can lid 2 and the like. Therefore, the defect inspection can be performed very efficiently. Further, by the angle detection means 14 and the illumination control means 19, even if the direction of the transported can lid 2 is uneven, the state in which the crack 10 or the crack 10 tends to be generated can be reliably processed as the depression 11. Thus, a highly accurate inspection can be performed.

Explanatory drawing which shows schematic structure of the defect inspection apparatus of one Embodiment of this invention. The explanatory perspective view of the principal part of this embodiment. Explanatory drawing which shows schematic structure of an illumination means. The flowchart which shows the action | operation of the defect inspection apparatus of this embodiment. Explanatory drawing which shows the reference | standard image of the back surface of a can lid. Explanatory drawing which shows the image of the can lid of a test object. Cross-sectional explanatory drawing of a part of can lid. Explanatory drawing which shows a test | inspection image. Explanatory top view which shows the front side of a can lid. Explanatory top view which shows the back side surface of a can lid.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Defect inspection apparatus, 2 ... Can lid (article), 3 ... Conveyance path, 4 ... Rivet, 5 ... Tab, 6 ... Score, 7 ... Breaking opening part, 11 ... Depression part, 12 ... 1st imaging means, 13 ... second imaging means, 14 ... angle detection means, 15 ... determination means, 17 ... second illumination means (illumination means), 18 ... third illumination means (other illumination means), 19 ... illumination control means, 20 ... light emission Part (light source).

Claims (9)

A defect inspection method for inspecting the presence or absence of a defect with an indented portion extending linearly generated at a predetermined position on the surface to be inspected for an article having the surface to be inspected,
A first imaging step of imaging the surface to be inspected;
Based on the image obtained by the first imaging step, an angle detection step of detecting the rotation angle of the article with the perpendicular passing through the center of the surface to be inspected as an axis;
An irradiation direction calculation step of calculating a light irradiation direction to the surface to be inspected from an angle detected by the angle detection step, with a direction intersecting a longitudinal direction of the hollow portion regarded as defective as a light irradiation direction; ,
A light irradiation step of irradiating light having directivity inclined toward the surface to be inspected from the direction calculated by the irradiation direction calculation step;
A second imaging step of imaging the surface to be inspected illuminated by the light irradiation step;
An inspection image generation step of generating an inspection image by extracting a region where the defect occurs from an image obtained by the second imaging step;
And a determination step of determining the presence or absence of the defect based on the image generated by the inspection image generation step.   In the light irradiation step, the light irradiated from the direction calculated in the irradiation direction calculation step includes a plurality of light sources arranged in a ring corresponding to the periphery of the surface to be inspected of the article, and selects each light source. 2. The defect inspection method according to claim 1, wherein the light is obtained by turning on only the light source corresponding to the direction calculated in the irradiation direction calculating step by a lighting device that can be turned on.   2. In the light irradiation step, another light having a light amount smaller than the light irradiated from the direction calculated in the irradiation direction calculation step is irradiated from a position opposed to the surface to be inspected. Or the defect inspection method of 2. The article is transported along a transport path;
The first imaging process is performed on the article conveyed to a predetermined position along the conveyance path, and the light irradiation process and the first are performed on the article conveyed to the downstream position through the first imaging process. The defect inspection method according to claim 1, wherein two imaging steps are performed. The article has a thin circular plate shape having a rupture opening portion that is fixed to a panel surface via a rivet, and is ruptured by a score at a position where the tip of the tab between the peripheral edge of the panel and the rivet faces. A can lid,
The panel back of the can lid is the surface to be inspected,
The defect determined by the determining step is a linear depression formed along the broken score along with the breaking of the score of the portion extending adjacent to the rivet. 5. The defect inspection method according to any one of 4 above. A defect inspection apparatus that inspects the presence or absence of a defect provided in a conveyance path that conveys an article, with a dent extending in a linear shape generated at a predetermined position on a surface to be inspected of the article conveyed along the conveyance path as a defect. There,
First imaging means for imaging a surface to be inspected of an article conveyed along the conveyance path;
An angle detection means for detecting the rotation angle of the article around the perpendicular line passing through the center of the surface to be inspected based on the image obtained by the first imaging means;
Provided on the downstream side of the first image pickup means, and on the surface to be inspected of an article conveyed through the first image pickup means, selectively from one direction around the surface to be inspected to the surface to be inspected. Illumination means capable of irradiating light having directivity that inclines toward
From the angle detected by the angle detection means, a direction intersecting with the longitudinal direction of the defective recess is calculated, and the calculated direction is used as the light irradiation direction to the surface to be inspected of the article. Lighting control means for controlling
Second imaging means for imaging the surface to be inspected of the article illuminated by the illumination means;
An inspection image is generated by extracting a region where the defect occurs from an image obtained by the second imaging unit, and a determination unit that determines presence / absence of the defect based on the generated image. Defect inspection equipment. The illumination means includes a plurality of light sources that are arranged in a ring and can be individually turned on,
The illumination control unit turns on only a light source corresponding to a direction intersecting with a longitudinal direction of the hollow portion that is determined to be defective calculated based on an angle detected by the angle detection unit. 6. The defect inspection apparatus according to 6.   The other illumination means for irradiating light having a light amount smaller than that of the illumination means from a position facing the surface to be inspected is provided at the position where the illumination means is provided. Defect inspection equipment. The article has a thin circular plate shape having a rupture opening portion that is fixed to a panel surface via a rivet, and is ruptured by a score at a position where the tip of the tab between the peripheral edge of the panel and the rivet faces. A can lid,
The panel back of the can lid is the surface to be inspected,
7. The defect determined by the determining means is a linear depression generated along a score that is broken along with a score break of a portion that extends adjacent to a rivet. The defect inspection apparatus according to any one of 8.

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